1. Field of the Invention
The present invention relates to an organic EL light emitting display device and a method of manufacturing the same.
2. Description of the Related Art
Recently, an electroluminescence (EL) light emitting display device using a multi-layered film of an organic material attracts attention. The organic EL light emitting display device comprises an organic light emitting layer sandwiched between an anode electrode formed of ITO and a cathode electrode. If a DC voltage is applied between the anode electrode and the cathode electrode, electrons are injected from the metal forming the cathode electrode into the low unoccupied molecular orbital (LUMO) of the organic compound constituting the electron transport layer. On the other hand, holes are injected from the ITO electrode constituting the anode electrode into the high occupied molecular orbital (HOMO) of the hole transport layer. As a result, the holes and the electrons are recombined within the organic light emitting layer so as to emit light. The method of manufacturing an organic EL light emitting display device can be roughly classified into two methods, i.e., into a method of the vapor deposition of molecules having a low molecular weight under vacuum and a method of coating a polymer solution.
In an organic EL light emitting display device, a metal having a low work function is used for forming the cathode electrode that is laminated on the organic light emitting layer because this enhances the efficiency of injecting electrons into the organic light emitting. However, the organic EL light emitting display device using a metal having a low work function for forming the cathode electrode is defective in that the organic EL light emitting display device tends to be degraded. It is impossible to obtain an organic EL light emitting display device having a sufficiently long life even if an inorganic compound layer (buffer layer) formed of a fluoride of an alkali metal or a fluoride of an alkaline earth metal is sandwiched between the organic light emitting layer and the cathode electrode.